The present invention is directed to polymer fibers comprising poly(ethylene oxide) compositions and methods of making polymer fibers comprising poly(ethylene oxide). More particularly, the present invention is directed to fibers comprising grafted poly(ethylene oxide) compositions.
Disposable personal care products such as pantiliners, diapers, tampons etc. are a great convenience. Such products provide the benefit of one time, sanitary use and are convenient because they are quick and easy to use. However, disposal of many such products is a concern due to limited landfill space. Incineration of such products is not desirable because of increasing concerns about air quality and the costs and difficulty associated with separating such products from other disposed, non-incineratable articles. Consequently, there is a need for disposable products which may be quickly and conveniently disposed of without dumping or incineration.
It has been proposed to dispose of such products in municipal and private sewage systems. Ideally, such products would be flushable and degradable in conventional sewage systems. Products suited for disposal in sewage systems and that can be flushed down conventional toilets are termed xe2x80x9cflushablexe2x80x9d herein. Disposal by flushing provides the additional benefit of providing a simple, convenient and sanitary means of disposal. Personal care products must have sufficient strength under the environmental conditions in which they will be used and be able to withstand the elevated temperature and humidity conditions encountered during use and storage yet still lose integrity upon contact with water in the toilet. Therefore, a water-disintegratable material which is thermally processable into fibers having mechanical integrity when dry is desirable.
Due to its unique interaction with water and body fluids, poly(ethylene oxide) (hereinafter PEO) is currently being considered as a component material in fibers and flushable products. PEO,
xe2x80x94(CH2CH2O)nxe2x80x94, 
is a commercially available water-soluble polymer that can be produced from the ring opening polymerization of the ethylene oxide, 
Because of its water-soluble properties, PEO is desirable for flushable applications. However, there is a dilemma in utilizing PEO in the fiber-making processes. PEO resins of low molecular weights, for example 200,000 g/mol. have desirable melt viscosity and melt pressure properties for extrusion processing but cannot be processed into fibers due to their low melt elasticities and low melt strengths. PEO resins of higher molecular weights, for example greater than 1,000,000 g/mol, have melt viscosities that are too high for fiber-spinning processes. These properties make conventional PEO difficult to process into fibers using conventional fiber-making processes.
PEO melt extruded from spinning plates and fiber spinning lines resists drawing and is easily broken. PEO resins do not form fibers using conventional melt fiber-making processes. As used herein, fibers are defined as filaments or threads or filament-like or thread-like structures with diameters of about 100 microns and less. Conventional PEO resins can only be melt processed into strands with diameters in the range of several millimeters. Therefore, PEO compositions with appropriate melt viscosities for processing fibers and with greater melt elasticities and melt strengths are desired.
In the personal care industry, flushable melt-spun fibers are desired for commercial viability and ease of disposal. PEO fibers have been produced by a solution casting process. However, it has not been possible to melt process PEO fibers using conventional fiber making techniques such as melt spinning. Melt processing techniques are more desirable than solution casting because melt processing techniques are more efficient and economical. Melt processing of fibers is needed for commercial viability. Prior art PEO compositions cannot be extruded into the melt with adequate melt strength and elasticity to allow attenuation of fibers. Presently, fibers cannot be produced from conventional PEO compositions by melting spinning.
Thus, currently available PEO resins are not practical for melt extrusion into fibers or for personal care applications. What is needed in the art, therefore, is a means to overcome the difficulties in melt processing of PEO resins so that PEO resins can be formed into fibers for later use as components in flushable, personal care products.
The present invention is directed to polymer fibers comprising PEO compositions and methods of making polymer fibers comprising PEO. More particularly, the present invention is directed to fibers comprising grafted PEO compositions. The modified PEO compositions have improved melt processability, allowing fibers to be drawn using conventional fiber-making techniques and apparatusses. The modification of the PEO resins is accomplished by grafting a polar vinyl monomer, such as a poly(ethylene glycol) methacrylate or 2-hydroxyethyl methacrylate, onto the PEO. The grafting is accomplished by mixing the PEO, the monomer(s) and a free radical initiator and applying heat. The resulting grafted PEOs have improved melt processability and may be used to melt process fibers using conventional fiber processing techniques.
To overcome the disadvantages of the prior art, this invention teaches fibers comprising PEO coplymers comprising grafted polar functional groups. Such modification of PEO reduces the melt viscosity and melt pressure of the PEO. The modified PEO resins can be solidified for later thermal processing into fibers or processed directly into fibers. The fibers are water soluble and are useful as components in personal care products.
As used herein, the term xe2x80x9cgraft copolymerxe2x80x9d means a copolymer produced by the combination of two or more chains of constitutionally or configurationally different features, one of which serves as a backbone main chain, and at least one of which is bonded at some point(s) along the backbone and constitutes a side chain. As used herein, the term xe2x80x9cgraftingxe2x80x9d means the forming of a polymer by the bonding of side chains or species at some point(s) along the backbone of a parent polymer. (See Sperling, L. H., Introduction to Physical Polymer Science 1986 pp. 44-47 which is incorporated by reference herein in its entirety.)
Modification of PEO in accordance with the invention improves the melt properties of PEO and allows the thermal processing of fibers from PEO. The modified PEO compositions have increased melt strength and increased melt elasticity yet have reduced melt viscosity. These changes make it possible to produce PEO fibers using conventional fiber processing methods. Modification of PEO resins with starting molecular weights of between about 50,000 g/mol to about 400,000 g/mol allows the PEO resin to be extruded into thin fibers using conventional melt spinning processes. Modification of PEO resins with starting molecular weights of between about 50,000 g/mol to about 300,000 g/mol is desirable and modification of PEO resins with starting molecular weights of between about 50,000 g/mol to about 200,000 g/mol is most desirable for fiber-making purposes. The modification of PEO in accordance with this invention improves the melt properties of the PEO allowing the modified PEO to be melted and attenuated into fibers. Thus, the modified PEO can be processed into water-soluble fibers using both meltblown and spunbond processes which are useful as components in liners, cloth-like outer covers, etc. in flushable personal care products.
These and other features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiments.